feat: add gRPC trace demonstration

Author: michal-kazmierczak

instrumentation/grpc/example/example_impl.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+# Copyright The OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+class ExampleImpl < ::Proto::Example::ExampleAPI::Service
+  def example(_req, _call)
+    Proto::Example::ExampleResponse.new(response_name: 'Hello')
+  end
+end

instrumentation/grpc/example/proto/example_api.proto

@@ -0,0 +1,16 @@
+syntax = "proto3";
+
+package proto.example;
+
+service ExampleAPI {
+  rpc Example(ExampleRequest) returns (ExampleResponse);
+}
+
+message ExampleRequest {
+  uint64 id = 1;
+  string name = 2;
+}
+
+message ExampleResponse {
+  string response_name = 1;
+}

instrumentation/grpc/example/proto/example_api_pb.rb

@@ -0,0 +1,35 @@
+require_relative './proto/example_api_services_pb'
+require_relative './example_impl'
+
+require 'bundler/inline'
+
+gemfile do
+  source 'https://rubygems.org'
+  gem 'grpc'
+  gem 'opentelemetry-api'
+  gem 'opentelemetry-common'
+  gem 'opentelemetry-instrumentation-grpc', path: '../'
+  gem 'opentelemetry-sdk'
+end
+
+ENV['OTEL_TRACES_EXPORTER'] = 'console'
+OpenTelemetry::SDK.configure do |c|
+  c.use 'OpenTelemetry::Instrumentation::Grpc'
+end
+
+
+# start the server
+@service = ExampleImpl.new
+server = GRPC::RpcServer.new(pool_size: 1, poll_period: 1)
+server_port = server.add_http2_port('localhost:0', :this_port_is_insecure)
+server.handle(ExampleImpl)
+server_thread = Thread.new { server.run }
+server.wait_till_running
+
+
+# make a request
+stub = Proto::Example::ExampleAPI::Stub.new("localhost:#{server_port}", :this_channel_is_insecure)
+stub.example(Proto::Example::ExampleRequest.new(id: 1, name: 'test!'))
+
+server.stop
+server_thread.join